My future mother-in-law insulted me at a family dinner?!?

A background here: me and my boyfriend met when we were both at college in london. we have been together for 3 years and a half and we decided we are going to get married but not right now because we want to be straight with our jobs and stuff and until we are ready financially. all my family lives back in honduras. he got a chance to go over there with me during vacations and all my family loved him. the problem is with my future mother-in-law. since the start she has given me a rough time. my boyfriend's dad loves me. i mean they all like me except her. so, last week we went to a dinner because it was my boyfriend's brother birthday. i arrived to his parents' house and everybody was welcoming except her. i wanted to shake my hand but she refused. and then while we were eating she said to me what i was doing with his son? which are my intentions? and i was confused. and she started saying that us latin american people are a disgrace and she thinks i am trying to take advantage of his son's family wealth. i was hysterical. i wanted to get off that seat and just go and punch her or something but i kept calm. i just got up and left. my boyfriend said that he asked his mom why did she say that. and he said that she doesn't like me because i am from a poor country. i do recognize that my boyfriend's family is like wealthy but that doesn't mean i lived in a poor home. i grew up in a decent home in a decent school. and i am currently working as a business consultant which pays you a LOT of money. so yeah... please help me .. i dont know what to do.. i want to tell her that she cannot control his son's life. he can make choices of his own and he is a grown man.